Liquid level detector

ABSTRACT

A liquid level detector may include a rotator fixed to an arm, a magnet fixed to the rotator, and a supporter rotatably supporting the rotator. The supporter may include a body, and an outer circumference wall disposed along a rotation direction of the arm on an outer circumference side of the magnet. The rotator may include a cover covering an end part of the outer circumference wall, and an opposing wall opposing at least one of an inner circumference surface and an outer circumference surface of the outer circumference wall. A first clearance between the supporter and the magnet may communicate with an outer space via a second clearance between the outer circumference wall and the cover and a third clearance between the outer circumference wall and the opposing wall. The first clearance may be larger than at least one of the second clearance and the third clearance.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent Application No.2015-020085 filed on Feb. 4, 2015, the contents of which are herebyincorporated by reference into the present application.

TECHNICAL FIELD

An art disclosed herein relates to a liquid level detector configured todetect a level of liquid (for example, a device configured to detect anamount of fuel stored in a fuel tank of an automobile or the like).

BACKGROUND

Japanese Patent Application Publication No. 2006-208211 discloses aliquid level detector that includes a float, an arm that revolves as thefloat moves, a body that has a revolving shaft of the arm, and a holderthat houses a cylindrical-shape magnet. The holder covers the revolvingshaft. A recessed portion is provided in the holder on an innercircumference side of the magnet, for allowing the revolving shaft to befitted thereinto. The revolving shaft is fitted into the recessedportion to thereby allow the recessed portion to function as a bearing.A magnetism detecting element is disposed at the revolving shaft, fordetecting changes in magnetic flux of the magnet that moves as therevolving arm revolves.

In this liquid level detector, a step portion of the body and/or aprojecting portion of the holder complicate a route from an outside ofthe liquid level detector to the revolving shaft. Metal powders or thelike in the fuel are thereby prevented from reaching the revolvingshaft.

SUMMARY

In the above-described liquid level detector, there is a possibilitythat, even if the route from an outside of the liquid level detector tothe revolving shaft is complicated, fine foreign substances may reachthe revolving shaft. When fine foreign substances accumulate around therevolving shaft, a clearance between the revolving shaft and the holderis clogged with the foreign substances, resulting in that the arm can nolonger revolve.

The present disclosure provides an art to suppress that foreignsubstances in a liquid interferes with a revolution of the arm.

The application discloses a liquid level detector. The liquid leveldetector may comprise: a float; an arm attached to the float andconfigured to convert a vertical motion of the float into a rotarymotion of the arm; a rotator configured of a resin and fixed to the armat a center of the rotary motion; a magnet fixed to the rotator; asupporter rotatably supporting the rotator; and a magnetic sensorcovered by the supporter and configured to output a signal correspondingto a rotation of the magnet opposing the magnetic sensor via thesupporter. The supporter may comprise: a body housing the magneticsensor; and an outer circumference wall projecting from the body towardthe rotator and disposed along a rotation direction of the arm on anouter circumference side of the magnet. The rotator may comprises: acover covering an end part of the outer circumference wall, the end partlocated opposite to the body; and an opposing wall opposing at least oneof an inner circumference surface and an outer circumference surface ofthe outer circumference wall and configured to slide relative to theouter circumference wall corresponding to the rotation of the arm. Aclearance between the supporter and the magnet may communicate with anouter space of the liquid level detector via a clearance between theouter circumference wall and the cover and a clearance between the outercircumference wall and the opposing wall The clearance between thesupporter and the magnet may be larger than at least one of theclearance between the outer circumference wall and the cover and theclearance between the outer circumference wall and the opposing wall.

In the above-described configuration, the clearance between thesupporter and the magnet is larger than at least one of the clearancebetween the outer circumference wall and the cover and the clearancebetween the outer circumference wall and the opposing wall. Largeforeign substances mixed with the fuel may not pass through theclearance between the outer circumference wall and the cover or theclearance between the outer circumference wall and the opposing wall,and hence may not reach the clearance between the supporter and themagnet. According to this configuration, relatively large foreignsubstances may be prevented from reaching the clearance between thesupporter and the magnet. Moreover, in the above-describedconfiguration, the rotator rotates while the outer circumference walland the opposing wall slide. In other words, the opposing wall functionsas a bearing of the rotator. The opposing wall and the outercircumference wall are opposed to each other on an outer circumferenceside of the magnet. According to this configuration, the opposing wall,which functions as the bearing, may be disposed at a position distantfrom the rotation center of the rotator, without making the magnetlarge. Consequently, with a vertical motion of the float, a relativelylarge moment may be generated at the opposing wall. Similarly, arelatively large moment may also be generated at the outer circumferencewall. Accordingly, even if foreign substances are caught in theclearance between the outer circumference wall and the opposing wall orthe clearance between the outer circumference wall and the cover, themoment generated by the vertical motion of the float can cause therotator to rotate. It is possible to suppress foreign substances in theliquid interfering with a revolution of the arm.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a configuration of a fuel supply system;

FIG. 2 shows a longitudinal cross-section of a magnetic sensor unit;

FIG. 3 shows an enlarged view of a region III of FIG. 2; and

FIG. 4 shows an enlarged view of a region at the same position as thatof the region III of FIG. 2 in the magnetic sensor unit in a variation.

DETAILED DESCRIPTION

Some features of embodiments described herein will be listed. Notably,technical features described herein are each independent technicalelement, and exhibit technical usefulness thereof solely or incombinations.

(Feature 1)

In a liquid level detector, an outer circumference surface of theopposing wall may oppose the inner circumference surface of the outercircumference wall. The clearance between the outer circumference walland the cover may be smaller than the clearance between the outercircumference wall and the opposing wall. In this configuration, theclearance between the outer circumference wall and the cover may belocated on the outer circumference side of the clearance between theouter circumference wall and the opposing wall. According to thisconfiguration, it is possible to suppress foreign substances enteringthe clearance between the outer circumference wall and the opposingwall.

(Feature 2)

In the liquid level detector, an outer circumference surface of theopposing wall may oppose the inner circumference surface of the outercircumference wall. The magnet may be disposed along an innercircumference surface of the opposing wall. A part of the clearancebetween the outer circumference wall and the opposing wall may be largerthan another part of the clearance between the outer circumference walland the opposing wall. If the foreign substances that have entered theclearance between the opposing wall and the outer circumference wall aresubstances adsorbed by the magnet, such as iron powders, the substancesare adsorbed by the magnet, which is held in the outer circumferencewall, in the clearance between the opposing wall and the outercircumference wall. Consequently, a part of the clearance between theopposing wall and the outer circumference wall can be increased tothereby store the foreign substances adsorbed by the magnet. It isthereby possible to suppress the foreign substances, which are adsorbedby the magnet, interfering with the rotation of the arm.

(Feature 3)

In the liquid level detector, a storing space may be disposed on a routefrom the outer space of the liquid level detector to the clearancebetween the supporter and the magnet, via the clearance between theouter circumference wall and the cover and the clearance between theouter circumference wall and the opposing wall. The storing space mayopen toward an inflow direction of the liquid flowing through the route.According to this configuration, the foreign substances that enter theroute can be stored in the storing space. It is thereby possible tosuppress the foreign substances accumulating in each clearance.

Representative, non-limiting examples of the present invention will nowbe described in further detail with reference to the attached drawings.This detailed description is merely intended to teach a person of skillin the art further details for practicing preferred aspects of thepresent teachings and is not intended to limit the scope of theinvention. Furthermore, each of the additional features and teachingsdisclosed below may be utilized separately or in conjunction with otherfeatures and teachings to provide improved liquid level detectors, aswell as methods for using and manufacturing the same.

Moreover, combinations of features and steps disclosed in the followingdetailed description may not be necessary to practice the invention inthe broadest sense, and are instead taught merely to particularlydescribe representative examples of the invention. Furthermore, variousfeatures of the above-described and below-described representativeexamples, as well as the various independent and dependent claims, maybe combined in ways that are not specifically and explicitly enumeratedin order to provide additional useful embodiments of the presentteachings.

All features disclosed in the description and/or the claims are intendedto be disclosed separately and independently from each other for thepurpose of original written disclosure, as well as for the purpose ofrestricting the claimed subject matter, independent of the compositionsof the features in the embodiments and/or the claims. In addition, allvalue ranges or indications of groups of entities are intended todisclose every possible intermediate value or intermediate entity forthe purpose of original written disclosure, as well as for the purposeof restricting the claimed subject matter.

As shown in FIG. 1, a fuel supply system 1 is a system configured tosupply, to an internal combustion engine not illustrated, fuel in a fueltank 4 mounted in an automobile. In the present embodiment, the fuel isgasoline, or a mixed fuel containing gasoline and alcohol (e.g.,ethanol). The fuel supply system 1 includes a fuel meter 60 and a fuelpump module 10. The fuel meter 60 is used for a display device of theautomobile, not illustrated. The fuel pump module 10 is disposed in thefuel tank 4. The fuel meter 60 and the fuel pump module 10 areelectrically connected by a plurality of lines 52, 54, and 56.

The fuel pump module 10 includes a fuel pump unit 12 and a fuel amountdetector 20. The fuel pump unit 12 is housed in the fuel tank 4. Thefuel pump unit 12 is attached to a set plate 6 configured to close anopening in the fuel tank 4. The fuel pump unit 12 sucks in the fuel inthe fuel tank 4, pressurizes the fuel thus sucked in, and discharges thefuel. The fuel discharged from the fuel pump unit 12 is supplied to theengine through a discharge port 14.

The fuel amount detector 20 includes a float 22, an arm 24 to which thefloat 22 is fixed, and a magnetic sensor unit 30 configured to detect arotation angle of the arm 24. The float 22 floats on the surface of thefuel in the fuel tank 4 and moves up and down depending on the liquidlevel of the fuel. The float 22 is rotatably attached to a leading endof the arm 24. A base end of the arm 24 is supported to be rotatablewith respect to the magnetic sensor unit 30. For this reason, when thefloat 22 moves up and down depending on the liquid level of the fuel inthe fuel tank 4, the arm 24 thereby swingably rotates with respect tothe fuel pump unit 12.

The arm 24 includes a float attachment part 24 a, a base part 24 b, anda fulcrum part 24 c. The float attachment part 24 a is configured of ametal that has a resistance to fuel, such as stainless steel, forexample. The float attachment part 24 a is configured of a columnarrod-like member bent at an intermediate position. The float 22 isattached to a leading end of the float attachment part 24 a. The basepart 24 b is fixed to a base end of the float attachment part 24 a.

The base part 24 b and the fulcrum part 24 c are configured of a resinhaving a resistance to fuel (e.g., a polyphenylene sulfide resin(hereinafter referred to as “PPS”)). The base part 24 b has a flat-plateshape. The fulcrum part 24 c is fixed to the base part 24 b at anintermediate position. The fulcrum part 24 c is rotatably supported bythe magnetic sensor unit 30.

As shown in FIGS. 1 and 2, the fulcrum part 24 c includes a cover 24 d,an opposing wall 24 e, and an engagement wall 24 f. Notably, FIG. 2shows a cross-sectional view of the magnetic sensor unit 30 and thefulcrum part 24 c, and is a cross-sectional view that represents across-section in vertical directions (the vertical directions of FIG.1), passing through a rotational axis X of FIG. 1. Moreover, thehorizontal directions of FIG. 2 correspond to the vertical directions ofFIG. 1. The cover 24 d has a disk shape. The rotational axis X of thearm 24 coincides with a rotational axis of the cover 24 d. The opposingwall 24 e projects on a surface of the cover 24 d on the magnetic sensorunit 30's side. The opposing wall 24 e has a cylindrical shape. Thecentral axis of the opposing wall 24 e coincides with the rotationalaxis X. On an outer circumference side of the opposing wall 24 e, theengagement wall 24 f is disposed with a spacing from an outercircumference surface of the opposing wall 24 e. The engagement wall 24f extends forming a circle along an outer circumference edge of thecover 24 d. An engagement flange 24 g of the engagement wall 24 f on themagnetic sensor unit 30's side extends toward the rotational axis X. Theengagement flange 24 g is disposed along the entire circumference of theengagement wall 24 f. Notably, in a variation, the engagement flange 24g may not be disposed along the entire circumference of the engagementwall 24 f. For example, one engagement flange 24 g may be disposed onlyat a portion of the engagement wall 24 f in a circumference direction,or a plurality of the engagement flanges 24 g may be disposed discretelyat the engagement wall 24 f in the circumference direction.

A magnet 26 is fitted into the inner circumference of the opposing wall24 e. The magnet 26 is fitted into an inner circumference surface of theopposing wall 24 e. The magnet 26 is a permanent magnet. The magnet 26has a disk shape. The center of the magnet 26 is located on therotational axis X. The magnet 26 has an N pole in one semicircular partand an S pole in the other semicircular part. The magnet 26 rotates asthe arm 24 swingably rotates. Consequently, an orientation of a magneticfield generated by the magnet 26 changes as the arm 24 swingablyrotates.

The magnetic sensor unit 30 revolvably supports the arm 24. As shown inFIG. 2, the magnetic sensor unit 30 includes a body 32, an outercircumference wall 34, a cover portion 46, a magnetic sensor 40, andlead wires 45 and 47.

The body 32 is configured of a material having a low permeability toalcohol (PPS in the present embodiment). At the body 32, the outercircumference wall 34 that receives a part of the fulcrum part 24 c ofthe arm 24 is disposed, the part housing the magnet 26. The outercircumference wall 34 has a cylindrical shape that has the central axisthat coincides with the rotational axis X. The outer circumference wall34 has an inner circumference flange 34 a that extends toward an innercircumference side and an outer circumference flange 34 b that extendstoward an outer circumference side, at an end opposite to the body 32.Each of the inner circumference flange 34 a and the outer circumferenceflange 34 b has an annular shape that encircles the rotational axis X.

The opposing wall 24 e is disposed on an inner circumference side of theouter circumference wall 34. An inner circumference surface of the outercircumference wall 34 and an outer circumference surface of the opposingwall 24 e are opposed to each other with a clearance. As shown in FIG.3, if the central axis of the outer circumference wall 34 and the centerof the cover 24 d are disposed on the rotational axis X, an innercircumference surface of the inner circumference flange 34 a of theouter circumference wall 34 and the outer circumference surface of theopposing wall 24 e are opposed to each other with a clearance CL3 thatencircles the rotational axis X. In a part where no inner circumferenceflange 34 a is disposed, in other words, in a part on the body 32's sidewith respect to the inner circumference flange 34 a, the innercircumference surface of the outer circumference wall 34 and the outercircumference surface of the opposing wall 24 e are opposed to eachother along the entire circumference of the rotational axis X, with aclearance CL2 that encircles the rotational axis X. The clearance CL2 islarger than the clearance CL3.

As shown in FIG. 2, the outer circumference flange 34 b engages with thefulcrum part 24 c. The arm 24 is thereby supported so as not to fall offfrom the magnetic sensor unit 30. In particular, an end of the outercircumference wall 34 opposite to the body 32 is wholly covered by thecover 24 d coupled to an end of the opposing wall 24 e opposite to thebody 32. The cover 24 d spreads toward the outer circumference side withrespect to the outer circumference wall 34. The outer circumference edgeof the cover 24 d is located on the outer circumference side of theouter circumference flange 34 b. The engagement wall 24 f that extendsfrom the outer circumference edge of the cover 24 d toward the body 32encircles the rotational axis X while being opposed to the outercircumference flange 34 b. The engagement flange 24 g disposed at an endof the engagement wall 24 f on the body 32's side is located on the body32′ side of the outer circumference flange 34 b.

As shown in FIG. 3, the fulcrum part 24 c and the outer circumferencewall 34 are disposed with clearances CIA to CL7 in between. Theclearance CIA is the one between an end of the outer circumference wall34 opposite to the body 32 and a surface of the cover 24 d on the body32's side. The clearance CL5 is the one between an outer circumferenceedge of the outer circumference flange 34 b and an inner circumferencesurface of the engagement wall 24 f. The clearance CL6 is the onebetween a surface of the outer circumference flange 34 b on the body 32′side and a surface of the engagement flange 24 g opposite to the body32. The clearance CL7 is the one between an inner circumference surfaceof the engagement flange 24 g and an outer circumference surface of theouter circumference wall 34.

Notably, a surface of the engagement flange 24 g on the body 32's sideis disposed with a clearance CL8 between itself and the body 32.

The body 32 houses the magnetic sensor 40. The magnetic sensor 40 ishoused in the body 32, while being covered by the cover portion 46. Thecover portion 46 is configured of a material having a low permeabilityto gasoline (an epoxy resin in the present embodiment). The coverportion 46 is housed in the body 32 by being disposed in a molding dieof the body 32, namely, by so-called insert molding, when the body 32 isto be molded.

The magnetic sensor 40 detects a rotary motion of the arm 24, and basedon that detected result, outputs to the fuel meter 60 a signal thatrepresents an analog amount corresponding to a liquid level of fuelstored in the fuel tank 4 (see FIG. 1). The signal that represents ananalog amount is, for example, an analog voltage signal, a signalthrough PWM (an abbreviation of Pulse Width Modulation), a signaltransmitted with use of digital communication such as CAN (anabbreviation of Controller Area Network) or LAN (an abbreviation ofLocal Area Network), and the like. The magnetic sensor 40 is amagnetic-type sensor that detects a rotation angle of the arm 24, and aknown sensor that utilizes a Hall IC, for example, can be used therefor.Specifically, the magnetic sensor 40 includes a detecting circuit 42,and an input/output circuit 44 connected to the detecting circuit 42.The detecting circuit 42 has a Hall element that detects an orientationof a magnetic field of the magnet 26. The input/output circuit 44 has acapacitor. The entire surface of the magnetic sensor 40 is covered bythe cover portion 46. The detecting circuit 42 is disposed on an endpart side of the cover portion 46. In particular, the detecting circuit42 is disposed at an end part opposite to an end on a side where thelead wire 47 described below penetrates the cover portion 46. Theinput/output circuit 44 is disposed approximately at the center of thecover portion 46.

The three lead wires 45 extend from the input/output circuit 44 on aside of the input/output circuit 44, opposite to the detecting circuit42. Upper end parts of the three lead wires 45 are connected to lowerend parts of the three lead wires 47, respectively. Upper end parts ofthe three lead wires 47 are connected to terminals 48 of the powersource line 52, the output line 54, and the ground line 56,respectively. The power source line 52, the output line 54, and theground line 56 penetrate the set plate 6 to thereby be connected to thefuel meter 60. The lead wires 45 and 47 and the terminals 48 areconfigured of a conductor having a high conductivity (copper in thepresent embodiment).

The magnetic sensor 40 is covered by the cover portion 46 by beingdisposed in a molding die of the cover portion 46, namely, by theso-called insert molding, when the cover portion 46 is to be molded. Thelead wires 45 are covered by the cover portion 46. Moreover, end partsof the lead wires 47 on the lead wires 45's side are covered by thecover portion 46. The lead wires 47 extend from connecting positions ofthe lead wires 47 and 45, respectively, in a direction separating awayfrom the magnetic sensor 40, penetrate the cover portion 46 and the body32, and are exposed to an outside of the body 32.

The fuel meter 60 has a CPU 64 and a display 62. The CPU 64 supplieselectric power to the fuel liquid level detector 20, particularly to themagnetic sensor 40, via the power source line 52. The signal output fromthe magnetic sensor 40 is input to the CPU 64 via the output line 54.The CPU 64 uses the signal input from the magnetic sensor 40, determinesan amount of fuel stored in the fuel tank 4, and displays on the display62 the fuel amount thus determined. The CPU 64 and the display 62 can beconfigured as in the ones in the conventionally-known fuel meter,respectively. Notably, the ground line 56 is grounded in the CPU 64.

(Liquid Amount Detecting Method)

Next, a liquid amount detecting method will be described. The CPU 64supplies electric power to the magnetic sensor 40 while the automobileis driven (i.e., while the engine is running). The magnetic sensor 40outputs a signal corresponding to an orientation of a magnetic field ofthe magnet 26. When the liquid level of the fuel in the fuel tank 4changes, the float 22 moves in vertical directions, and the arm 24rotates as the float 22 moves in the vertical directions. The magnet 26rotates on its own axis as the arm 24 rotates. Consequently, theorientation of the magnetic field of the magnet 26 changes depending onthe rotation of the arm 24, in other words, the liquid level of the fuelin the fuel tank 4. Accordingly, the signal output from the magneticsensor 40 is correlated with the liquid level of the fuel in the fueltank 4.

When the signal output from the magnetic sensor 40 is input to the CPU64, the CPU 64 determines an amount of fuel stored in the fuel tank 4,and displays on the display 62 the fuel amount thus determined. Inparticular, the CPU 64 uses a database or a function that is stored inthe CPU 64 and shows a relation between a signal output from themagnetic sensor 40 and a fuel amount, to thereby determine the fuelamount. The database or the function is predetermined by execution of anexperiment or a simulation, and stored in the CPU 64.

(Relations Among the Clearances CL1 to CL8)

The clearance CL1 between the body 32 and the magnet 26 is surrounded bythe outer circumference wall 34. The clearance CL1 communicates with anouter space of the fuel liquid level detector 20 via the clearances CL2to CL8.

In the state where the fulcrum part 24 c is located at a referenceposition in a direction vertical to the rotational axis X (i.e., asshown in FIG. 2, a position where the central axis of the magnet 26supported by the fulcrum part 24 c coincides with the central axis ofthe outer circumference wall 34), a width of the clearance CL3(hereinafter referred to as a “width W1”) is provided to extend so as toform a circle along a rotation direction of the arm 24. At this time,each of the clearances CL5 and CL7 (hereinafter referred to as a “widthW1+α”) is larger than the clearance CL3.

The opposing wall 24 e and the inner circumference flange 34 a slide tothereby cause the arm 24 to rotate relative to the body 32. In otherwords, the opposing wall 24 e functions as a bearing of the arm 24.According to this configuration, the bearing of the arm 24 can bedisposed at an outer circumference of the magnet 26. Consequently,without making the magnet 26 large, a diameter of the bearing can beincreased.

If the arm 24 rotates, the size of the clearance CL3 becomes 0 at asliding section of the opposing wall 24 e and the inner circumferenceflange 34 a, whereas the width of the clearance CL3 becomes twice aslarge as the width W1 (hereinafter referred to as “W1×2”) at a sectionopposite to that sliding section with the rotational axis X interposedtherebetween. On the other hand, the width of each of the clearances CL5and CL7 becomes a width W1+α+W1 on an outer circumference side of theposition where the width of the clearance CL3 is a width 0, and becomesa width a on an outer circumference side of the position where the widthof the clearance CL3 is the width W1×2.

In the state where the fulcrum part 24 c is located at a referenceposition in a rotational axis X's direction (i.e., a position where theclearances CIA and CL6 are identical), the width of each of theclearances CIA and CL6 (hereinafter referred to as a width “W2”) issmaller than the width of the clearance CL1 (hereinafter referred to asa width “W3”), and smaller than the width of the clearance CL8(hereinafter referred to as a width “W4”). Moreover, if the fulcrum part24 c is located at the reference position in the rotational axis X'sdirection, the width W3 of the clearance CL1 is smaller than the widthW4 of the clearance CL8. In this configuration, the fulcrum part 24 cmoves relative to the magnetic sensor unit 30 in the rotational axis X'sdirection, by a width twice as large as the width W2 of the clearancesCIA and CL6.

In the situation where the fulcrum part 24 c is located both at thereference position in the direction vertical to the rotational axis X,and at the reference position in the rotational axis X's direction, thewidth W2 of each of the clearances CIA and CL6 is smaller than the widthW1 of the clearance CL3.

In the configuration in the present embodiment, as shown by an arrow ofFIG. 3, the fuel passes through the clearances CL8, CL7, CL6, CL5, CL4,CL3, and CL2 in this order, and reaches the clearance CL1. If foreignsubstances are mixed with the fuel, the foreign substances pass throughthe clearance CL8. A storing groove 34 c that opens toward the clearanceCL8 is disposed in the outer circumference wall 34. The storing groove34 c is disposed to extend so as to form a circle along the rotationdirection of the arm 24. The foreign substances that have passed throughthe clearance CL8 flow into the storing groove 34 c along a flow of thefuel. A portion of the foreign substances mixed with the fuel is therebystored in the storing groove 34 c. Consequently, it is possible tosuppress the foreign substances entering the clearances CL1 to CL7,which are located downstream of the clearance CL8.

Moreover, it is possible to suppress the foreign substances that are notstored in the storing groove 34 c and flow downstream from the clearanceCL7 entering downstream of the clearance CIA, by means of the clearancesCL6 and CIA that have a relatively small width. Consequently, theforeign substances can be prevented from entering the clearances CL1 toCL3.

Furthermore, when the arm 24 rotates, a larger moment is generated inthe clearances CL6 and CIA than in the clearances CL1 to CL3.Accordingly, hindrance to the arm 24's rotation due to foreignsubstances being caught in the arm 24's clearances can be prevented moreeffectively in the case where the foreign substances are caught in theclearances CL6 and CIA than in the case where the foreign substances arecaught in the clearances CL1 to CL3.

Out of the foreign substances that have reached downstream of theclearance CL3, the ones adsorbed by the magnet, such as iron powders,are adsorbed by the magnet 26 onto the outer circumference surface ofthe opposing wall 24 e. The clearance CL2, which has a width larger thanthat of the clearance CL3, is disposed downstream of the clearance CL3.The foreign substances adsorbed by the magnet 26 are stored in theclearance CL2. It is thereby possible to suppress the foreign substancesadsorbed by the magnet 26 from being caught in the clearances CL2 andCL3.

(Variation 1)

In the above-described embodiment, the opposing wall 24 e and the innercircumference flange 34 a slide to thereby cause the arm 24 to rotaterelative to the body 32. However, the engagement wall 24 f and the outercircumference flange 34 b may slide to thereby cause the arm 24 torotate relative to the body 32. In this case, the width of the clearanceCL5 may be smaller than that of each of the clearances CL3 and CL7. Inthe present variation, the engagement wall 24 f is an example of the“opposing wall”. In the present variation, the inner circumferencesurface of the outer circumference wall 34 may not be opposed to theopposing wall 24 e.

(Variation 2)

In the above-described embodiment, in the case where the fulcrum part 24c is located at the reference position in the direction vertical to therotational axis X, the width of the clearance CL3 is larger than that ofeach of the clearances CL5 and CL7. However, the width of the clearanceCL3 may be identical to at least one of the widths of the clearances CL5and CL7. If the width of the clearance CL3 is identical to the width ofthe clearance CL5, the opposing wall 24 e and the inner circumferenceflange 34 a may slide and the engagement wall 24 f and the outercircumference flange 34 b may slide, to thereby cause the arm 24 torotate relative to the body 32. If the width of the clearance CL3 isidentical to the clearance CL7, the opposing wall 24 e and the innercircumference flange 34 a may slide and the engagement wall 24 f(particularly the engagement flange 24 g) and the outer circumferencewall 34 may slide, to thereby cause the arm 24 to rotate relative to thebody 32.

(Variation 3)

In the above-described embodiment, in the case where the fulcrum part 24c is located both at the reference position in the direction vertical tothe rotational axis X and at the reference position in the rotationalaxis X's direction, the width of each of the clearances CL1 to CL8 isentirely uniform. However, the width of each of the clearances CL1 toCL8 may not be entirely uniform. For example, the width of the clearanceCL2 may be identical to the width of the clearance CL3, partially in therotation direction of the arm 24.

(Variation 4)

In the above-described embodiment, the engagement wall 24 f extends soas to form a circle along the outer circumference edge of the cover 24d. However, the engagement wall 24 f may not extend as aforementionedalong the outer circumference edge of the cover 24 d, and may bedisposed discretely at the outer circumference edge of the cover 24 d.

(Variation 5)

In the above-described embodiment, the storing groove 34 c is formed atan end of the outer circumference wall 34 on the body 32's side.However, the position of the storing groove 34 c is not limited thereto.For example, the storing groove 34 c may be formed in the outercircumference flange 34 b. In this case, the storing groove 34 c mayopen toward the clearance CL7.

(Variation 6)

In each of the above-described embodiments, the magnet 26 is exposedfrom the fulcrum part 24 c. However, the magnet 26 may be housed in thefulcrum part 24 c. In the present variation, a clearance between thebody 32 and a surface of the fulcrum part 24 c on the body 32's sidethat covers a surface of the magnet 26 on the body 32's side is anexample of the “clearance between the supporter and the magnet”.

(Variation 7)

The “liquid level detector” in the present disclosure may be a devicethat detects an amount of liquid in a container, for example, an amountof water stored in a water storage tank, and the like, other than thefuel amount detector 20 that detects the amount of fuel in the fuel tank4.

(Variation 8)

In the above-described embodiment, the magnetic sensor 40 outputs to thefuel meter 60 a signal related to an analog amount corresponding to aliquid level of the fuel stored in the fuel tank 4. The CPU 64 in thefuel meter 60 then uses the signal that has been output from themagnetic sensor 40 and represents the analog amount, to determine a fuelamount. However, the magnetic sensor 40 may convert the analog amountcorresponding to the liquid level of the fuel stored in the fuel tank 4into a fuel amount, and output to the CPU 64 a signal corresponding tothe fuel amount. The magnetic sensor 40 may convert the analog amountinto the fuel amount, with a technique similar to that of the CPU 64 inthe above-described embodiment. The CPU 64 may determine the fuel amountfrom the signal corresponding to the fuel amount, which has been inputfrom the magnetic sensor 40, and display on the display 62 the fuelamount thus determined.

(Variation 9)

In the above-described embodiment, the opposing wall 24 e of the arm 24has a cylindrical shape that has a uniform thickness along therotational axis X's direction. However, the cylindrical shape may nothave a uniform thickness along the direction of the rotational axis X ofthe opposing wall 24 e. For example, as shown in FIG. 4, at the opposingwall 24 e, two cylindrical portions 124 and 125 that have widthsdifferent from each other may be disposed adjacently in the rotationalaxis X's direction. The cylindrical portion 124 may be disposed on thecover 24 d's side, in other words, on an upstream side, of thecylindrical portion 125. An inner diameter of the cylindrical portion124 may be equal to an inner diameter of the cylindrical portion 125,and an outer diameter of the cylindrical portion 124 may be larger thanan outer diameter of the cylindrical portion 125. In this case, theouter circumference wall 34 may not have the inner circumference flange34 a. In other words, the outer circumference wall 34 may have an innercircumference surface that is spaced from the rotational axis X by aconstant distance on its entire surface. The clearance CL2′ between theinner circumference surface of the outer circumference wall 34 and anouter circumference surface of the cylindrical portion 125 may be largerthan a clearance CL3′ between the inner circumference surface of theouter circumference wall 34 and an outer circumference surface of thecylindrical portion 124.

What is claimed is:
 1. A liquid level detector comprising: a float; anarm attached to the float and configured to convert a vertical motion ofthe float into a rotary motion of the arm; a rotator configured of aresin and fixed to the arm at a center of the rotary motion; a magnetfixed to the rotator; a supporter rotatably supporting the rotator; anda magnetic sensor covered by the supporter and configured to output asignal corresponding to a rotation of the magnet opposing the magneticsensor via the supporter, wherein the supporter comprises: a bodyhousing the magnetic sensor; and an outer circumference wall projectingfrom the body toward the rotator and disposed along a rotation directionof the arm on an outer circumference side of the magnet, the rotatorcomprises: a cover covering an end part of the outer circumference wall,the end part located opposite to the body; and an opposing wall opposingat least one of an inner circumference surface and an outercircumference surface of the outer circumference wall and configured toslide relative to the outer circumference wall corresponding to therotation of the arm, a clearance between the supporter and the magnetcommunicates with an outer space of the liquid level detector via aclearance between the outer circumference wall and the cover and aclearance between the outer circumference wall and the opposing wall,and the clearance between the supporter and the magnet is larger than atleast one of the clearance between the outer circumference wall and thecover and the clearance between the outer circumference wall and theopposing wall.
 2. The liquid level detector as in claim 1, wherein anouter circumference surface of the opposing wall opposes the innercircumference surface of the outer circumference wall, and the clearancebetween the outer circumference wall and the cover is smaller than theclearance between the outer circumference wall and the opposing wall. 3.The liquid level detector as in claim 1, wherein an outer circumferencesurface of the opposing wall opposes the inner circumference surface ofthe outer circumference wall, the magnet is disposed along an innercircumference surface of the opposing wall, and a part of the clearancebetween the outer circumference wall and the opposing wall is largerthan another part of the clearance between the outer circumference walland the opposing wall.
 4. The liquid level detector as in claim 1,wherein a storing space is disposed on a route from the outer space ofthe liquid level detector to the clearance between the supporter and themagnet, via the clearance between the outer circumference wall and thecover and the clearance between the outer circumference wall and theopposing wall, and the storing space opens toward an inflow direction ofthe liquid flowing through the route.
 5. The liquid level detector as inclaim 1, wherein the opposing wall is disposed outside of the outercircumference wall, an inner circumference surface of the opposing wallopposes the outer circumference surface of the outer circumference wall,and the clearance between the outer circumference wall and the cover issmaller than the clearance between the outer circumference wall and theopposing wall.
 6. The liquid level detector as in claim 5, whereinanother opposing wall is further disposed inside of the outercircumference wall, an outer circumference surface of the other opposingwall opposes the inner circumference surface of the outer circumferencewall, and the clearance between the outer circumference wall and thecover is smaller than the clearance between the outer circumference walland the other opposing wall.
 7. The liquid level detector as in claim 5,wherein the outer circumference wall comprises an outer circumferenceflange extending toward an outer circumference side of the outercircumference wall, and the opposing wall comprises an engagement flangeextending toward an inner circumference side of the opposing wallbetween the outer circumference flange and the body.
 8. The liquid leveldetector as in claim 7, wherein a clearance between the outercircumference wall and the engagement flange is smaller than theclearance between the supporter and the magnet.